(i) Field of the invention
This invention relates to a process for coating a preformed base material and to the coated preformed base material so provided
(ii) Description of the Prior Art
DE-As No. 1238199 disclose a film of isobutyl rubber which is used to cover and line containers. This film consists of two laminated, integral layers, one of which is adapted to be bonded by adhesion to the wall of the container to be lined.
The periodical "KAUTSCHUK+GUMMI. KUNSTSTOFFE" No. 2, 1980, page 95 to 100 teaches the application of rubber to containers, filters, pipes, valves, pumps and the like as a surface protection against corrosion. For this purpose, self-vulcanizing types of rubber are used, which are applied at low temperatures without surface pressure. However, according to the teachings of this publication, all holes and unevenesses of the base material, e.g. the surfaces of concrete, must be smoothed and sealed prior to the application of the rubber.
European Patent No. 0,009,053 (corresponding to U.S. Pat. No. 4,562,103) teaches a process for the production of weather-resistant slabs or shaped bodies. In such process, wood particles, or lignocellulose fibres, or other fibrous raw materials were mixed with binding agents, were covered with a layer of vulcanizable rubber or other elastomer and were pressed at high temperatures. This process, however, can not be applied in all cases, e.g. in those cases where the deformation and the hardening of the material were not a result of the material being exposed simultaneously to pressure and high temperatures, but instead were the result of predominantly cold chemical reactions occuring during the setting process. For this reason, in that process a different step must be taken here in the timing and mechanical separation of the production of material and the coating process.
Preformed panels or shaped slabs of light-weight concrete or porous concrete, or insulating slabs made of expanded clay, asbestos cement, asbestos fibres, or gypsum have been known a long time. These preformed panels are widely used as building material for outside and inside wall coverings, facings and roofs because of their flame resistance and rot resistance.
There are, however, limits to their use, mainly because of their weight and the extreme brittleness of the material. Any attempt to reduce the thickness of this material and to increase the size of the slabs, is met by an increased brittleness, which did not permit the use of thin slabs of the desirable larger size. Thus necessitated costly safety measures during mounting and construction at the building site.
It has been proposed to provide a protective and/or decorative surface treatment to such mineral material slabs. However, at the present time, multiple steps of repeated coating and drying procedures are required during which liquid film-forming coats or prefabricated adhesive coating materials are applied. All of these, however, have the disadvantage that they are not suited for permanent use. Often therefore, after a short period of time detachment of the surface coating occurs. This may result from adhesive fatique in the adhesive coating material which is applied to metal sheets, or plywood sheets which is helped along by changes in climate, temperature and dimensions. Coatings which have been applied in liquid form tend to dry out and crack, whereafter moisture enters by creeping underneath the coating, thereby detaching it. Even if weathering does not attack or destroy the material as such, the reliability and the protective function of the coating is no longer guaranteed. Furthermore, the alkaline content of inorganic binding agents generally has an anti-adhesive effect, unless such effect is neutralized or eliminated by creating special surfaces and layers, and by using very expensive adhesives or coating systems.
These difficulties exist to a very high degree in connection with the use of elastomers. Up to the present time no process is known which would guarantee a permanent, weather-resistant bonding of vulcanized elastomers, to mineral materials which are generally alkaline, by industrial production methods at economically justifiable costs. However, such group of elastomeric materials are particularly suited to be used for outer coatings of building material in an excellent manner, due to their weather resistance and color fastness, their lasting resilience and the possibility to be utilized at thicknesses which are physically effective which make them superior to other materials.